Collaborative sign-on

1. A method, comprising: responsive to a user providing at least one authentication credential to a second system during an attempt to log into a first online account hosted by the second system, receiving, by a first system comprising at least one processor, an authentication approval request from the second system; responsive to receiving the authentication approval request from the second system, determining, by the first system, whether the user is required to be logged into at least a second online account hosted by at least a third system unrelated to the second system in order to approve the authentication approval request; responsive to determining that the user is required to be logged into at least the second online account hosted by at least the third system in order to approve the authentication approval request, determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session; responsive to determining that the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session, communicating to the second system a response to the authentication approval request indicating that the user is approved for authentication with the second system to log into the first online account hosted by the second system; responsive to the user providing at least one authentication credential to a fourth system during an attempt to log into a third online account hosted by the fourth system, receiving, by the first system, a second authentication approval request from the fourth system; responsive to receiving the second authentication approval request from the fourth system, determining, by the first system, whether the user is required to be logged into at least a fourth online account hosted by at least a fifth system unrelated to the fourth system in order to approve the second authentication approval request; responsive to determining that the user is required to be logged into at least the fourth online account hosted by at least the fifth system in order to approve the authentication approval request, determining, by the first system, whether the user presently is logged into at least the fourth online account hosted by at least the fifth system in at least one presently active user session; and responsive to determining that the user presently is not logged into at least the fourth online account hosted by the at least the fifth system in at least one presently active user session, communicating to the fourth system a response to the authentication approval request indicating that the user is not approved for authentication with the fourth system to log into the third online account hosted by the fourth system.

2. The method of claim 1 , wherein determining, by the first system, whether the user is required to be logged into at least a second online account hosted by at least a third system unrelated to the second system in order to approve the authentication approval request comprises: determining whether the user is required to be logged into at least a second online account hosted by at least a third system unrelated to the second system in order to approve the authentication approval request by accessing, by the first system, log-in rules established for the user and processing, by the first system, the log-in rules.

3. The method of claim 1 , wherein determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session comprises: communicating, by the first system, a log-in status request message to at least the third system, the log-in status request requesting the user's log-in status with the third system; and determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session by receiving from at least the third system a login status message, the log-in status message indicating whether the user presently is logged into at least the second online account hosted by the third system in at least one presently active user session.

4. The method of claim 1 , wherein determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session comprises: accessing, by the first system, a data structure stored to memory elements, the data structure tracking whether the user presently is logged into at least the second online account; and determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session by processing data accessed from the data structure.

5. The method of claim 1 , wherein determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session comprises: periodically polling, by the first system, at least the third system to inquire whether the user presently is logged into at least the second online account hosted by at least the third system; and receiving, by the first system, status messages indicating whether the user presently is logged into at least the second online account hosted by at least the third system.

6. A first system, comprising: a processor programmed to initiate executable operations comprising: responsive to a user providing at least one authentication credential to a second system during an attempt to log into a first online account hosted by the second system, receiving, by the first system, an authentication approval request from the second system; responsive to receiving the authentication approval request from the second system, determining, by the first system, whether the user is required to be logged into at least a second online account hosted by at least a third system unrelated to the second system in order to approve the authentication approval request; responsive to determining that the user is required to be logged into at least the second online account hosted by at least the third system in order to approve the authentication approval request, determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session; responsive to determining that the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session, communicating to the second system a response to the authentication approval request indicating that the user is approved for authentication with the second system to log into the first online account hosted by the second system; responsive to the user providing at least one authentication credential to a fourth system during an attempt to log into a third online account hosted by the fourth system, receiving, by the first system, a second authentication approval request from the fourth system; responsive to receiving the second authentication approval request from the fourth system, determining, by the first system, whether the user is required to be logged into at least a fourth online account hosted by at least a fifth system unrelated to the fourth system in order to approve the second authentication approval request; responsive to determining that the user is required to be logged into at least the fourth online account hosted by at least the fifth system in order to approve the authentication approval request, determining, by the first system, whether the user presently is logged into at least the fourth online account hosted by at least the fifth system in at least one presently active user session; and responsive to determining that the user presently is not logged into at least the fourth online account hosted by the at least the fifth system in at least one presently active user session, communicating to the fourth system a response to the authentication approval request indicating that the user is not approved for authentication with the fourth system to log into the third online account hosted by the fourth system.

7. The first system of claim 6 , wherein determining, by the first system, whether the user is required to be logged into at least a second online account hosted by at least a third system unrelated to the second system in order to approve the authentication approval request comprises: determining whether the user is required to be logged into at least a second online account hosted by at least a third system unrelated to the second system in order to approve the authentication approval request by accessing, by the first system, log-in rules established for the user and processing, by the first system, the log-in rules.

8. The first system of claim 6 , wherein determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session comprises: communicating, by the first system, a log-in status request message to at least the third system, the log-in status request requesting the user's log-in status with the third system; and determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session by receiving from at least the third system a login status message, the log-in status message indicating whether the user presently is logged into at least the second online account hosted by the third system in at least one presently active user session.

9. The first system of claim 6 , wherein determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session comprises: accessing, by the first system, a data structure stored to memory elements, the data structure tracking whether the user presently is logged into at least the second online account; and determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session by processing data accessed from the data structure.

10. The first system of claim 6 , wherein determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session comprises: periodically polling, by the first system, at least the third system to inquire whether the user presently is logged into at least the second online account hosted by at least the third system; and receiving, by the first system, status messages indicating whether the user presently is logged into at least the second online account hosted by at least the third system.

11. A computer program product comprising a computer readable storage medium having program code stored thereon, the program code configured to, when executed by a processor, perform operations comprising: responsive to a user providing at least one authentication credential to a second system during an attempt to log into a first online account hosted by the second system, receiving, by a first system comprising the processor, an authentication approval request from the second system; responsive to receiving the authentication approval request from the second system, determining, by the first system, whether the user is required to be logged into at least a second online account hosted by at least a third system unrelated to the second system in order to approve the authentication approval request; responsive to determining that the user is required to be logged into at least the second online account hosted by at least the third system in order to approve the authentication approval request, determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session; and responsive to determining that the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session, communicating to the second system a response to the authentication approval request indicating that the user is approved for authentication with the second system to log into the first online account hosted by the second system; responsive to the user providing at least one authentication credential to a fourth system during an attempt to log into a third online account hosted by the fourth system, receiving, by the first system, a second authentication approval request from the fourth system; responsive to receiving the second authentication approval request from the fourth system, determining, by the first system, whether the user is required to be logged into at least a fourth online account hosted by at least a fifth system unrelated to the fourth system in order to approve the second authentication approval request; responsive to determining that the user is required to be logged into at least the fourth online account hosted by at least the fifth system in order to approve the authentication approval request, determining, by the first system, whether the user presently is logged into at least the fourth online account hosted by at least the fifth system in at least one presently active user session; and responsive to determining that the user presently is not logged into at least the fourth online account hosted by the at least the fifth system in at least one presently active user session, communicating to the fourth system a response to the authentication approval request indicating that the user is not approved for authentication with the fourth system to log into the third online account hosted by the fourth system.

12. The computer program product of claim 11 , wherein determining, by the first system, whether the user is required to be logged into at least a second online account hosted by at least a third system unrelated to the second system in order to approve the authentication approval request comprises: determining whether the user is required to be logged into at least a second online account hosted by at least a third system unrelated to the second system in order to approve the authentication approval request by accessing, by the first system, log-in rules established for the user and processing, by the first system, the log-in rules.

13. The computer program product of claim 11 , wherein determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session comprises: communicating, by the first system, a log-in status request message to at least the third system, the log-in status request requesting the user's log-in status with the third system; and determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session by receiving from at least the third system a login status message, the log-in status message indicating whether the user presently is logged into at least the second online account hosted by the third system in at least one presently active user session.

14. The computer program product of claim 11 , wherein determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session comprises: accessing, by the first system, a data structure stored to memory elements, the data structure tracking whether the user presently is logged into at least the second online account; and determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session by processing data accessed from the data structure.

15. The computer program product of claim 11 , wherein determining, by the first system, whether the user presently is logged into at least the second online account hosted by at least the third system in at least one presently active user session comprises: periodically polling, by the first system, at least the third system to inquire whether the user presently is logged into at least the second online account hosted by at least the third system; and receiving, by the first system, status messages indicating whether the user presently is logged into at least the second online account hosted by at least the third system.